Visible crew/equipment: After John gets dressed in his cell Rygel points out John's cellmate, and when Aeryn removes her helmet we can see a nice reflection of the reflector screen, which is on the same side as the cell doors.
Visible crew/equipment: After John successfully instructs Aeryn on how to maneuver and slingshot Moya away from the PK's Command Carrier, Zhaan gives John a very special thank you. When it cuts to the DRD scooting across the floor in Moya's empty Command, a crew member wearing shorts can be seen at the right side of the screen, as he's looking in the direction of the DRD, and is presumably controlling the DRD's remote control.
Chosen answer: It's never explained. John mentions a theory that his less technologically developed craft simply interferes with the wormhole less than the "superior" Vipers, but they never make a concrete determination on that point. But we also have to take into account the fact that Moya traverses wormholes with no ill effect as well.
Garlonuss ★